Abstract

The regulation of α-fetoprotein (AFP) secretion and growth rate by various hormones in established human hepatoma (HuH-7, PLC/PRF/5, huH-1, huH-4, and KIM-1/c-4) and hepatoblastoma (HUH-6 Clone 5) cell lines was studied. These 6 cell lines replicated continuously in a chemically defined medium and secreted 84 ng (HuH-7) to 23 pg (huH-4) AFP per 24 h per 1 × 104 cells into the culture medium. The addition of insulin increased the growth rate of all examined cell lines and partially inhibited the AFP secretion in those cell lines except KIM-1/c-4, while the addition of dexamethasone inhibited the growth and stimulated the AFP secretion in all of the cell lines. The addition of 3,3′,5-triiodothyronine inhibited the growth of all cell lines; however, different effects on the AFP secretion were observed depending on the cell lines used. Obviously, the AFP secretion was unrelated to the change in growth rate. When dexamethasone and N6-O2-dibutyryl cyclic AMP were added together, the AFP secretion was further stimulated. On the other hand, when dexamethasone and insulin were added simultaneously, the dexamethasone-mediated stimulation of AFP secretions was diminished. The data indicated that the regulatory mechanisms of AFP secretion by the hormones in the established human hepatoma and hepatoblastoma cell lines cannot be deduced according to the results of one cell line.